1. Field of the Invention
The present invention relates to a plasma etching device used for wafer etching or the like in a semiconductor device manufacturing process.
2. Description of the Related Art
As a wafer etching device used in a semiconductor device manufacturing process, there is known a plasma etching device for etching (dry-etching) a wafer mounted on a cathode electrode using plasma by applying RF power to an upper electrode (anode electrode) and a lower electrode (cathode electrode) arranged to face each other in an evacuated process chamber to generate plasma between the anode and cathode electrodes while supplying etching gas which contains chlorine gas (Cl2) into the process chamber.
The plasma etching device stated above is known as follows. If a plurality of wafers are continuously etched, an etching quantity, i.e., etching rate for the wafers per unit time changes (increases or decreases) over time in accordance with an increase in the number of processed wafers even if etching conditions including the RF power applied to the electrodes and the quantity of the etching gas supplied into the process chamber are controlled to be constant. The etching rate change is considered to be caused by changes over time (normally increases) in the ambient temperature of the interior of the process chamber and the temperatures of various members including the electrodes, a gas ring for supplying the process gas, the inner wall surface of the process chamber and the like due to the plasma and the heat generated from the electrodes during etching, and by changes in the composition and density of the plasma and the quantity of deposits adhering to the inner wall surface of the process chamber due to these temperature changes.
Some conventional plasma etching device has a cooler and a heater provided at electrodes or the wall portion of the process chamber so as to prevent etching rate from changing according to an increase in the number of processed wafers, and has a temperature sensor for detecting the temperatures of the electrodes, the wall portion of the process chamber and the like, arranged therein. The plasma etching device controls the temperatures of the electrodes and the inner wall portion of the process chamber to be constant based on the temperatures detected by the temperature sensor, and thereby suppresses the change of etching rate due to the increase in the number of processed wafers.
Further, a plasma film formation device for forming an insulating film on a substrate within a vacuum bath using plasma gas is disclosed by Japanese Patent Application Laid-Open (JP-A) No. 2000-345348, page 4, FIG. 1 and the like. In the plasma film formation device, in cases where insulating films are continuously formed on a plurality of substrates, cooling gas such as N2 is supplied to a shower plate provided with a gas port for supplying film formation gas into the vacuum bath after the completion of forming a film on the preceding substrate and before the subsequent substrate is transported into the vacuum bath, and the cooling gas is introduced into the vacuum bath through the gas port of the shower plate, whereby increases in the ambient temperature of the interior of the vacuum bath and the temperature of the shower plate are suppressed.
However, the conventional plasma etching device which adjusts the temperatures of the members such as the electrodes and the wall portion of the process chamber using the cooler and the heater as described above, has the following disadvantage. The device can adjust the temperatures of these members themselves to respective target temperatures with high accuracy within relatively a short period of time. However, since the adjustment is made only using the heat conducted from these members, it is difficult to adjust the ambient temperature of the interior of the process chamber to the target temperature within a short period of time after the completion of etching one wafer and before the start of etching the next wafer.
Further, the plasma film formation device disclosed by the JP-A No. 2000-345348 has the following disadvantage. It is possible to efficiently decrease the ambient temperature of the interior of the vacuum bath and the temperature of the shower plate within a short period of time by introducing the cooling gas into the vacuum bath through the gas port of the shower plate. However, these temperatures cannot be accurately adjusted to respective target temperatures. That is, only by introducing the cooling gas into the vacuum bath for a certain period after the completion of forming a film on a preceding substrate and before the delivery of a subsequent substrate into the vacuum bath, it is impossible to accurately adjust the ambient temperature of the interior of the vacuum bath and the temperature of such a member as the shower plate that faces the interior of the vacuum bath to respective target temperatures if the quantity of the heat emitted when plasma is generated within the vacuum bath differs among the substrates or if the temperatures of the vacuum bath and the like rise over time due to by a regenerative reaction or the like.